stage1/init: mirror host's /etc/localtime symlink target in rootfs

This suppresses the warning when systemd-nspawn tries recreating the host's
/etc/localtime symlink in the container filesystem.
systems where this isn't a link systemd-nspawn will throw a warning:
/etc/localtime is not a symlink, not updating container timezone.

fakesdboot.so could be utilized to lie to nspawn if it becomes necessary.  Arguably systemd-nspawn should copy the file when it's not a link if it's really determined to propagate the locatime into the container.